You might see what a local jeweller recommends. A product specifically meant for fine jewelry would effectively clean the surface while being gentle enough to do so without inadvertently causing surface damage.

I've used a bit of toothpaste and a cotton cloth to remove heavy tarnish from some cheap sterling silver jewelry, but there's a risk of creating tiny surface scratches because it's abrasive, giving a cloudy appearance over time. So I probably would not use that on ferrules/fittings on pipes, as I would want them to stay nice and shiny.